Beta Lactam Antibiotics

Mode of action:

Inhibition of cell wall synthesis. This particular
group is characterized by its four-membered, nitrogen-containing
beta-lactam ring at the core of their structure, which is key to the
mode of action of this group of antibiotics. Beta lactam
antibiotics target the penicillin-binding proteins or PBPs - a group of
enzymes found anchored in the cell membrane, which are involved in the
cross-linking of the bacterial cell wall. The beta-lactam ring portion
of this group of antibiotics binds to these different PBPs, rendering
them unable to perform their role in cell wall synthesis. This
then leads to death of the bacterial cell due to osmotic instability or
autolysis.

Although beta – lactam antibiotics should theoretically work against
all types of bacteria, this is not the case. This is because
different bacteria have varying PBP content and nature. Also, some
bacteria have natural structural characteristics which does not favor
this mode of action (e.g., Gram-negatives have an outer membrane layer
which makes the PBPs more difficult to reach).